An Atlantic City, N.J., jury on Monday awarded $18 million in compensatory damages to a former user of the painkiller Vioxx, and $2 million to his wife, finding Merck & Co.’s failure to warn of the drug’s cardiovascular risks substantially contributed to his heart attack.

The eight-member jury deliberated for five hours before handing up its finding that Frederick Humeston’s doctor could have warned him about the risks had he known about them before Merck changed its label in April 2002.